Golf is governed by The Rules of Golf as approved by the United States Golf Association and the Royal and Ancient Golf Club of St. Andrews, Scotland, referred to herein as the USGA Rules. The most current rules are available from www.USGA.org. A typical game of golf is played on a course having 18 holes and a golfer may carry up to fourteen clubs with him during play. An average golfer uses over 80 strokes to complete the game, and typically half of those stokes are putts. Therefore, the putter is by far the most important of the regulation 14 golf clubs in a golfer's bag, and improved putting will improve a player's score more than improvement in any other stroke.
Consequently, thousands of devices and methods have been devised to help a golfer improve his putting, ranging from the practical to the absurd. Most of these devices do not conform to the design of clubs specified by the USGA Rules, however, and therefore are used during practice only. The golfer must switch putters to play a round of golf, thus changing the primary tool with which he perfected his stroke. As a result, the putt stokes during play are seldom as good as during practice. It would be advantageous, then, to provide a dual-purpose putter that conforms to the USGA Rules so that the golfer can use the same putter in practice as in play.
Under the USGA Rules, the putter shall have a shaft and a head, fixed to form one unit. When the golf club is in its normal position to address the ball, the shaft shall be aligned so that the projection of the straight part of the shaft onto the vertical plane through the toe and heel shall diverge from the vertical by at least 10 degrees. Further, the projection of the straight part of the shaft onto the vertical plane along the intended line of play shall not diverge from the vertical by more than 20 degrees. The USGA Rules further require that the clubhead meet specific criteria. For example, the distance from the heel to the toe of a putter shall be greater than the distance from the play face to the back. These rules limit the orientation of the shaft to the clubhead, and therefore the balance of the putter, a major factor in aligning the ball and in putting consistently.
The penalty for playing a game of golf with a putter that does not conform to the USGA Rules is disqualification from the game. However, with the many rules pertaining to the design of putters, it is difficult to design a club that provides quality training features for practicing and yet can be used for play. It is desirable to provide a single putter that can be converted from a practice putter to a play putter that conforms to USGA Rules.
For putters that are convertible from practice to play, one of the most difficult USGA Rules to comply with relates to “providing a putter with a shaft and a head, fixed to form one unit.” The fit between the clubhead and shaft must be extremely tight as to be essentially one unit.
It would also be desirable for a golfer to practice with putters of various weights to determine which weight makes the most accurate puts. Further, as a golfer's stroke changes over time, the golfer may want to change the weight of the putter. While a golfer can buy several putters each of a different weight, multiple putters are expensive and each one has its own characteristics that require the golfer to practice with to become accurate. It would be desirable to have a single putter that allows the golfer to change its weight.
During the putt stroke, the clubhead passes above the solid ground by only a very short distance. The length and density of the grass on each green may vary, causing the friction against the putter to vary accordingly. It would be desirable to have nearly constant friction against the putter on every green, so that a uniform putt stroke could be used from green to green. One way to make the friction as constant as possible is to reduce it as much as possible.
Therefore, it is an object of the present invention to provide a putter with a clubhead that is capable of rotating from a first position to strike the ball with a practice face to a second position to strike the ball with play face in which the shaft and clubhead that are fixed so securely that they form essentially one unit. It is another object of this invention to provide a putter that enables the golfer to change its weight. It is another object to provide a putter in which the friction between the clubhead and grass is minimized. It is also an object of this invention to provide a putter that enables the golfer to determine which strokes are the best during practice so that he may practice those strokes repeatedly and learn to stroke the ball consistently in play. It is another object of this invention to provide a single putter that can be used for both practice and play. It is a further object of this invention to provide a putter in which the shaft always diverges at least 10 degrees from the sole of the clubhead, regardless which orientation the golfer holds the putter when addressing the ball.